I am running QGIS 2.8 on a Mac machine and I want to calculate the catchment area using SAGA - Catchment Area. It starts running but after a while when QGIS wants to open the generated files there is an error message that QGIS cannot open the files:

Oooops! The following output layers could not be open
Name for output filled (flooded) elevation raster map:
/var/folders/g1/r0fk8c2j5ddf7p5jf_1x851w0000gn/T/processing/b30a24aad2ba451abc6875ff7ec46740/filled.tif
Name for output flow direction raster map:
/var/folders/g1/r0fk8c2j5ddf7p5jf_1x851w0000gn/T/processing/93e5878769d84ebc981bfb3721b1a861/direction.tif
Name for output sink-watershed raster map:

Are you just running the tool straight, or as part of a model/processing chain? I seem to recall having this sort of issue using the exact same SAGA cachement area when using it inside a processing chain, which required a hacky workaround.
– ThomasOct 16 '15 at 19:10